Optically detected magnetic resonance spectroscopy of rhodium (III) mixed-chelate complexes

Abstract

An optically detected magnetic resonance study of the lowest excited state of [Rh(thpy) (phpy) (bpy)] +, doped into a single crystal of [Rh(phpy) 2(bpy)]PF 6, is reported. Here, thpy −=2,2′-thienylpyridine, phpy −=2-phenylpyridine and bpy=2,2′-bi-pyridine. In emission, the dopant molecule gives rise to two zero-phonon lines, at 519.9 and 517.9 nm, respectively. The two zero-phonon lines are characteristic of the two structurally inequivalent forms of the dopant complex in the crystal lattice. From zero-and low-field ODMR data it is concluded that the lowest excited state in each of the two complex conformations is a phosphorescent triplet state. The fine structure splittings and the orientation of the fine structure tensor main axes of the triplet states of the two complex conformations are found to be different. It is argued that for both conformations the lowest excited state is a thpy −-localized 3ππ* state.